Method of forming polyaryl polymers

ABSTRACT

In a method of forming a polyacetal or polyketal, a specific acetal- or ketal-containing bis(aryl)acetal is coupled with itself or a comonomer in the presence of a catalyst and a base. The polymerization reaction tolerates hydroxyl and other functional groups on the bis(aryl)acetal. Among other applications, the polyacetals and polyketals are useful components of photoresist compositions.

FIELD

The present invention relates to a method of synthesizing polyaryl polymers, in particular polyacetals and polyketals.

INTRODUCTION

Polyacetals are known polymers that have has some use in microlithography. (As used herein, for brevity and except as otherwise noted, the term “acetal” shall be understood to be generic to “acetal” and “ketal”, the term “oligoacetal” shall be understood to be generic to “oligoacetal” and “oligoketal”, and the term “polyacetal” shall be understood to be generic to “polyacetal” and “polyketal”.) The synthesis of polyacetals typically relies on a polycondensation reaction to form acetal moieties during the polymerization reaction. The polycondensation reactants include free or protected hydroxyl groups that are consumed in the acetal formation, so the resulting polymers do not typically contain free hydroxyl groups or other functional groups that would interfere with or be consumed in the typical acetal formation reactions.

There is a need for materials and methods than can be used to synthesize oligoacetals and polyacetals. It would be desirable if the methods were general to the formation of oligoacetals and polyacetals with and without free hydroxyl groups and other functional groups that are incompatible with polycondensation conditions.

SUMMARY

One embodiment is a method of forming a polymer, the method comprising: reacting a monomer in the presence of a catalyst and a base to form a polymer; wherein the monomer comprises a bis(aryl)acetal having the structure

wherein Y¹ and Y² are each independently chloro, bromo, iodo, mesylate, tosylate, triflate, or B^(x), wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar¹ or Ar² via a boron atom; Ar¹ and Ar² are each independently unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene; and R¹ and R² are each independently hydrogen, unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl; unsubstituted or substituted C₆₋₁₈ aryl, or unsubstituted or substituted C₃₋₁₈ heteroaryl; and R¹ and R² are optionally covalently linked to each other to form a ring that includes —R¹—C—R²—, where the central carbon is the acetal carbon; wherein when one of Y¹ and Y² is chloro, bromo, iodo, triflate, mesylate, or tosylate, and the other of Y¹ and Y² is B^(x), the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², R¹, and R² are defined above, and each occurrence of Ar¹, Ar², R¹, and R² is defined independently; wherein when Y¹ and Y² are each B^(x), the monomer further comprises a bis(leaving group)arylene having the structure X—Ar³—X wherein each occurrence of X is independently chloro, bromo, iodo, triflate, mesylate, or tosylate; wherein Ar³ is unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently; and wherein when Y¹ and Y² are each independently selected from chloro, bromo, iodo, triflate, mesylate, or tosylate, the monomer further comprises a bis(boron-containing functional group)arylene having the structure B^(x)—Ar³—B^(x) wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar³ via a boron atom; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently.

This and other embodiments are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents superimposed proton nuclear magnetic resonance (¹H-NMR) spectra of the Preparative Example 3 polymer in acetone-d₆ without (solid) or with (dotted) D₂O.

FIG. 2 presents superimposed ¹H-NMR spectra of the Preparative Example 3 polymer untreated (solid) and sodium hydroxide-treated (dotted) in THF-d₈.

DETAILED DESCRIPTION

The present method of forming polyacetals by catalyzed polymerization of bis(aryl)acetals can exhibit one or more of the following advantages relative to acetal-forming polycondensation methods and known Suzuki coupling or polymerization methods: the present method can be conducted at or near ambient temperature, it is compatible with monomers containing functional groups that are incompatible with acetal-forming polycondensation methods, such as phenols and base-labile functional groups such as acetate esters, it is capable of producing polymers, and it tolerates certain functional groups, such as ortho-alkoxy groups or free phenol groups in an aryl dihalide, that depress some Suzuki coupling and polycondensation reactions. It is important to note functional groups that only slightly depress bimolecular Suzuki coupling can be detrimental for Suzuki polycondensation reactions and significantly reduce product molecular weight. It is further important to note that in bimolecular coupling reactions it is always possible to increase yield by increasing the ratio of one of the coupling partners, which is not an option in Suzuki coupling and polycondensation reactions. Finally, it is known in the art that reaction conditions that are particularly favorable for bimolecular Suzuki reactions are not necessarily the best ones for Suzuki polymerization reactions.

As used herein, “substituted” means including at least one substituent such as a halogen (i.e., F, Cl, Br, I), hydroxyl, amino, thiol, carboxyl, carboxylate, amide, nitrile, sulfide, disulfide, nitro, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxyl, C₆₋₁₈ aryl, C₆₋₁₈ aryloxyl, C₇₋₁₈ alkylaryl, or C₇₋₁₈ alkylaryloxyl. It will be understood that any group or structure disclosed with respect to the formulas herein may be so substituted unless otherwise specified, or where such substitution would significantly adversely affect the desired properties of the resulting structure. Also, “fluorinated” means having one or more fluorine atoms incorporated into the group. For example, where a C₁₋₁₈ fluoroalkyl group is indicated, the fluoroalkyl group can include one or more fluorine atoms, for example, a single fluorine atom, two fluorine atoms (e.g., as a 1,1-difluoroethyl group), three fluorine atoms (e.g., as a 2,2,2-trifluoroethyl group), or fluorine atoms at each free valence of carbon (e.g., as a perfluorinated group such as —CF₃, —C₂F₅, —C₃F₇, or —C₄F₉).

One embodiment is a method of forming a polymer, the method comprising: reacting a monomer in the presence of a catalyst and a base to form a polymer; wherein the monomer comprises a bis(aryl)acetal having the structure

wherein Y¹ and Y² are each independently chloro, bromo, iodo, mesylate, tosylate, triflate, or B^(x), wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar¹ or Ar² via a boron atom; Ar¹ and Ar² are each independently unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene; and R¹ and R² are each independently hydrogen, unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl; unsubstituted or substituted C₆₋₁₈ aryl, or unsubstituted or substituted C₃₋₁₈ heteroaryl; and R¹ and R² are optionally covalently linked to each other to form a ring that includes —R¹—C—R²—; wherein when one of Y¹ and Y² is chloro, bromo, iodo, triflate, mesylate, or tosylate, and the other of Y¹ and Y² is B^(x), the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², R¹, and R² are defined above, and each occurrence of Ar¹, Ar², R¹, and R² is defined independently; wherein when Y¹ and Y² are each B^(x), the monomer further comprises a bis(leaving group)arylene having the structure X—Ar³—X wherein each occurrence of X is independently chloro, bromo, iodo, triflate, mesylate, or tosylate; wherein Ar³ is unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently; and wherein when Y¹ and Y² are each independently selected from chloro, bromo, iodo, triflate, mesylate, or tosylate, the monomer further comprises a bis(boron-containing functional group)arylene having the structure B^(x)—Ar³—B^(x) wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar³ via a boron atom; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently.

The method utilizes a bis(aryl)acetal having the structure shown above. In the bis(aryl)acetal structure, when one of Y¹ and Y² is chloro, bromo, iodo, triflate, mesylate, or tosylate, and the other of Y¹ and Y² is B^(x), then the bis(aryl)acetal can be coupled to itself (homopolymerized) to form a polymer comprising a plurality of repeat units having the structure

wherein Ar¹, Ar², R¹, and R² are defined above, and each occurrence of Ar¹, Ar², R¹, and R² is defined independently (that is, different species of the bis(aryl)acetal having Y¹ and Y² as defined here can be copolymerized). In some embodiments, Y² is chloro or bromo. In some embodiments Y² is bromo. As used herein, the term “plurality” means at least three. Also, the term “polymer” will be understood to encompass oligomers comprising as few as three repeat units. The desired number of repeat units will depend on the intended use of the polymer. For example, when the polymer is used in a photoresist composition, it may be desirable for the polymer to comprise at least 5 repeat units, specifically 5 to 200 repeat units. when one of Y¹ and Y² is chloro, bromo, iodo, triflate, mesylate, or tosylate, and the other of Y¹ and Y² is B^(x), then the bis(aryl)acetal can, optionally, be copolymerized with a compound having the structure B^(x)—Ar³—X

wherein B^(x), Ar³, and X are defined above. This copolymerization yields a polymer comprising a plurality of repeat units having the structure

wherein Ar¹, Ar², R¹, and R² are defined above and each occurrence of Ar¹, Ar², R¹, and R² is defined independently; and a plurality of repeat units having the structure *

Ar³

*

wherein Ar³ is defined above and each occurrence of Ar³ is defined independently. In the context, it should be noted that the repeat units having the structure

need not be adjacent to each other, and the plurality of repeat units having the structure *

Ar³

* need not be adjacent to each other. In other words, the copolymer can be a random copolymer.

In other embodiments, when Y¹ and Y² are each B^(x), then the bis(aryl)acetal is copolymerized with a bis(leaving group)arylene having the structure X—Ar³—X wherein X and Ar³ are defined above. The resulting polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently.

In still other embodiments, when Y¹ and Y² are each independently selected from chloro, bromo, iodo, triflate, mesylate, or tosylate, then the bis(aryl)acetal is copolymerized with a bis(boron-containing functional group)arylene having the structure B^(x)—Ar³—B^(x) wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar³ via a boron atom; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently

Whether present in the bis(aryl)acetal, the compound having the structure B^(x)—Ar³—X or the bis(boron-containing functional group)arylene having the structure B^(x)—Ar³—B^(x) each occurrence of B^(x) is independently a boron-containing functional group bonded to the adjacent Ar¹, Ar², or Ar³ via a boron atom. Examples of B^(x) groups include —BF₃ ⁻M⁺, wherein each occurrence of M⁺ is independently an alkali metal cation, or an unsubstituted or substituted ammonium ion; —B(OH)₂; and

wherein R³ and R⁴ are each independently C₁₋₁₈ alkyl, C₃₋₁₈ cycloalkyl, or C₆₋₁₈ aryl; and R³ and R⁴ are optionally covalently linked to each other to form a ring that includes —R³—O—B—O—R⁴—.

In some embodiments, each occurrence of B^(x) is independently

wherein R³ and R⁴ are each independently C₁₋₁₈ alkyl, C₃₋₁₈ cycloalkyl, or C₆₋₁₈ aryl; and R³ and R⁴ are optionally covalently linked to each other to form a ring that includes —R³—O—B—O—R⁴—.

Examples of B^(x) species include

In the bis(aryl)acetal structure above, Ar¹ and Ar² are each independently unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene. In some embodiments, Ar¹ and Ar² are not covalently linked to each other to form a ring structure that includes —Ar¹—O—C—O—Ar²—. In other embodiments, Ar¹ and Ar² are covalently linked to each other, for example via a second acetal group, to form a ring structure that includes —Ar¹—O—C—O—Ar²—. Specific examples of Ar¹ and Ar² include unsubstituted or substituted 1,2-phenylene, unsubstituted or substituted 1,3-phenylene, unsubstituted or substituted 1,4-phenylene, unsubstituted or substituted 4,4′-biphenylene, unsubstituted or substituted 4,4″-p-terphenylene, unsubstituted or substituted 3,3″-p-terphenylene, unsubstituted or substituted 4,4″-m-terphenylene, unsubstituted or substituted 4,4″-p-terphenylene, unsubstituted or substituted 4,4″-o-terphenylene, unsubstituted or substituted 2,2″-o-terphenylene, unsubstituted or substituted 1,4-naphthylene, unsubstituted or substituted 2,7-naphthylene, unsubstituted or substituted 2,6-naphthylene, unsubstituted or substituted 1,5-naphthylene, unsubstituted or substituted 2,3-naphthylene, unsubstituted or substituted 1,7-naphthylene, unsubstituted or substituted 1,8-naphthylene, unsubstituted or substituted imidazo-2,4-ylene, 2,4-pyridylene, 2,5-pyridylene, unsubstituted or substituted 1,8-anthracenylene, unsubstituted or substituted 9,10-anthracenylene, unsubstituted or substituted 2,7-phenanthrenylene, unsubstituted or substituted 9,10-phenanthrenylene, unsubstituted or substituted 3,6-phenanthrenylene, unsubstituted or substituted 2,7-pyrenylene, unsubstituted or substituted 1,6-pyrenylene, unsubstituted or substituted-1,8-pyrenylene, unsubstituted or substituted 2,5-furanylene, unsubstituted or substituted 3,4-furanylene, unsubstituted or substituted 2,3-furanylene, unsubstituted or substituted 2,5-thiofuranylene, unsubstituted or substituted 3,4-thiofuranylene, unsubstituted or substituted 2,3-thiofuranylene, unsubstituted or substituted 2,5-oxazolylene, unsubstituted or substituted 2,7-fluorenylene, unsubstituted or substituted 2,5-benzofuranylene, unsubstituted or substituted 2,7-benzofuranylene, unsubstituted or substituted 5,7-benzofuranylene, unsubstituted or substituted 5,7-[1,3-benzoxazole], unsubstituted or substituted dithieno[3,2-b:2′,3′-d]thiophene, and unsubstituted or substituted 2,7-xanthenylene.

In some embodiments, at least one of Ar¹, Ar², and Ar³ is substituted with at least one functional group selected from the group consisting of hydroxyl, acetals, ketals, esters, and lactones.

In some embodiments, in at least one of the repeat units of the polymer, at least one of R¹, R², Ar¹, Ar² and Ar³ (when present) is substituted with hydroxyl. In some embodiments, at least 10 mole percent of repeat units in the polymer comprise at least one hydroxyl. Within the limit, the mole percent of repeat units in the polymer comprising at least one hydroxyl can be up to 40, 60, 80, 90, or 95. In some embodiments, at least one of R¹, R², Ar¹, Ar², and Ar³ (when present) is substituted with hydroxyl in at least 40 mole percent of the plurality of repeat units. In some embodiments, in 40 to 99 mole percent of the plurality of repeat units at least one of Ar¹, Ar², and Ar³ (when present) is substituted with hydroxyl, and in 1 to 60 mole percent of the plurality of repeat units at least one of Ar¹, Ar² and Ar³ is substituted with the acetal or ketal. A preferred acetal is —O—C(H)(R⁵)—OR⁶, wherein R⁵ is methyl and R⁶ is cyclohexyl. In some embodiments, each occurrence of Ar¹, Ar², and Ar³ is independently 1,3-phenylene or 1,4-phenylene.

The acetals can be monovalent acetals having the structure —O—C(H)(R⁵)—OR⁶, wherein R⁵ and R⁶ are independently selected from the group consisting of unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, and unsubstituted or substituted C₃₋₁₈ heteroaryl. In some embodiments, R⁵ and R⁶ are covalently connected to each others to form a ring structure. In some embodiments, R⁵ or R⁶ is covalently connected to the polymer backbone (e.g., via bonding to R¹ or R², or to one of Ar¹, Ar², and Ar³ to which the oxygen end of the acetal is not already bound). In these embodiments, the acetal is part of a ring structure. The ring structure can include or not include Ar¹—O—C—O—Ar². Specific examples of monovalent acetals having the structure —O—C(H)(R⁵)—OR⁶ include

The acetals can also be divalent cyclic acetals attached via oxygen atoms to Ar¹, Ar², or Ar³ as shown in the structure

wherein Ar^(n) is Ar¹, Ar², or Ar³ (when present), or a combination of Ar¹ and Ar² (for example, when one acetal oxygen is bonded directly to Ar¹ and the other directly to Ar²) or a combination of Ar² and Ar³; R¹⁰ is selected from the group consisting of unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, and unsubstituted or substituted C₃₋₁₈ heteroaryl. In some embodiments, the cyclic acetal is part of a ring structure that includes Ar¹—O—C(R¹)(R²)—O—Ar². In other embodiments, the cyclic acetal is not part of such a ring structure.

The ketals can be monovalent ketals having the structure —O—C(R⁷)(R⁸)—OR⁹, wherein R⁷, R⁸, and R⁹ are independently selected from the group consisting of unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, and unsubstituted or substituted C₃₋₁₈ heteroaryl. Optionally R⁷, R⁸, or R⁹ is covalently connected to the polymer backbone such that the acetal is part of a ring structure.

The ketals can also be cyclic ketals attached via oxygen atoms to Ar¹ or Ar² as shown in the structure

wherein Ar^(n) is Ar¹ or Ar², or a combination of Ar¹ and Ar² (for example, when one ketal oxygen is bonded directly to Ar¹ and the other directly to Ar²); R¹¹ and R¹² are independently selected from the group consisting of unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, and unsubstituted or substituted C₃₋₁₈ heteroaryl. In some embodiments, the cyclic ketal is part of a ring structure that includes Ar¹—O—C(R¹)(R²)—O—Ar². In other embodiments, the cyclic ketal is not part of such a ring structure.

The esters can have the structure —(O)_(a)-(L¹)_(b)-C(═O)—OR¹³, wherein a is 0 or 1 and b is 0 or 1, provided that when a is 1 then b is 1; R¹³ is selected from the group consisting of unsubstituted or substituted C₁₋₂₀ linear or branched alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, diphenylmethyl, 2-phenylpropan-2-yl, 1,1-diphenylethan-1-yl, triphenylmethyl), unsubstituted or substituted C₃₋₂₀ cycloalkyl (e.g., cyclopentyl, cyclohexyl, methylcyclohexan-1-yl, ethylcyclohexan-1-yl, 1-norbornyl, 1-adamantlyl, 2-methylbicyclo[2.2.1]heptan-2-yl, 1-adamantlyl, 2-methyladamantan-2-yl), unsubstituted or substituted C₆₋₂₀ aryl (e.g., phenyl, 1-naphthyl, and 2-naphthyl), and unsubstituted or substituted C₃₋₂₀ heteroaryl (e.g., 2-imidazolyl, 4-imidazolyl, 2-pyridyl, 3-pyridyl, and 4-pyridyl); and wherein L¹ is selected from the group consisting of unsubstituted or substituted C₁₋₂₀ linear or branched alkylene (e.g., methane-1,1-diyl (—CH₂—), ethane-1,2-diyl (—CH₂CH₂—), ethane-1,1-diyl (—CH(CH₃)—), propane-2,2-diyl(—C(CH₃)₂—)), unsubstituted or substituted C₃₋₂₀ cycloalkylene (e.g., 1,1-cyclopentanediyl, 1,2-cyclopentanediyl, 1,1-cyclohexanediyl, 1,4-cyclohexanediyl), unsubstituted or substituted C₆₋₂₀ arylene (e.g., 1,3-phenylene, 1,4-phenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene), and unsubstituted or substituted C₃₋₂₀ heteroarylene (e.g., imidazo-2,4-ylene, 2,4-pyridylene, 2,5-pyridylene). In some embodiments, R¹³ and L¹ are covalently connected to each others to form a lactone. In some embodiments, R¹³ is bonded to the adjacent ester oxygen atom via a tertiary carbon atom, for example,

Alternatively, the esters can have the structure —(O)_(c)—(L²)_(d)-O—C(═O)—R¹⁴, wherein c is 0 or 1 and d is 0 or 1, provided that when c is 1 then d is 1; R¹⁴ is selected from the group consisting of unsubstituted or substituted C₁₋₂₀ linear or branched alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, diphenylmethyl, 2-phenylpropan-2-yl, 1,1-diphenylethan-1-yl, and triphenylmethyl), unsubstituted or substituted C₃₋₂₀ cycloalkyl (e.g., cyclopentyl, cyclohexyl, 1-norbornyl, 1-adamantlyl, 2-methylbicyclo[2.2.1]heptan-2-yl, 2-methyladamantan-2-yl), unsubstituted or substituted C₆₋₂₀ aryl (e.g., phenyl, 1-naphthyl, 2-naphthyl), and unsubstituted or substituted C₃₋₂₀ heteroaryl (e.g., 2-imidazolyl, 4-imidazolyl, 2-pyridyl, 3-pyridyl, 4-pyridyl); and wherein L² is selected from the group consisting of unsubstituted or substituted C₁₋₂₀ linear or branched alkylene (e.g., methane-1,1-diyl (—CH₂—), ethane-1,2-diyl (—CH₂CH₂—), ethane-1,1-diyl (—CH(CH₃)—), propane-2,2-diyl (—C(CH₃)₂—), 2-methylpropane-1,2-diyl(—CH₂C(CH₃)₂—), diphenylmethylene (—C(C₆H₅)₂—), 1-phenylmethane-1,1-diyl (—CH(C₆H₅)—), 2-phenylpropane-1,2-diyl (—CH₂C(CH₃)(C₆H₅)—), 1,1-diphenylethane-1,2-diyl(—CH₂C(C₆H₅)₂)—), unsubstituted or substituted C₃₋₂₀ cycloalkylene (e.g., 1,1-cyclopentanediyl, 1,2-cyclopentanediyl, 1,1-cyclohexanediyl, 1,4-cyclohexanediyl, ethylcyclohexane-1,4-diyl, 4-methyladamantane-1,4-diyl), unsubstituted or substituted C₆₋₂₀ arylene (e.g., 1,3-phenylene, 1,4-phenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene), and unsubstituted or substituted C₃₋₂₀ heteroarylene (e.g., imidazo-2,4-ylene, 2,4-pyridylene, 2,5-pyridylene). In some embodiments, R¹⁴ and L² are covalently connected to each others to form a lactone. A specific example of an ester having the structure —(O)_(c)-(L²)_(d)-O—C(═O)—R¹⁴ is

The lactones can have the structure

wherein e is 0 or 1; f is 0 or 1; g is 1, 2, 3, or 4 (specifically 2); R⁵⁰ is hydrogen, unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, or unsubstituted or substituted C₃₋₁₈ heteroaryl; and L³ is selected from the group consisting of unsubstituted or substituted C₁₋₂₀ linear or branched alkylene (e.g., unsubstituted or substituted C₃₋₂₀ cycloalkylene (e.g., 1,1-cyclopentanediyl, 1,2-cyclopentanediyl, 1,1-cyclohexanediyl, 1,4-cyclohexanediyl), unsubstituted or substituted C₆₋₂₀ arylene (e.g., 1,3-phenylene, 1,4-phenylene, 1,4-naphthylene, 1,5-naphthylene, 2,6-naphthylene), and unsubstituted or substituted C₃₋₂₀ heteroarylene (e.g., imidazo-2,4-ylene, 2,4-pyridylene, 2,5-pyridylene).

In some embodiments, in at least one of the repeat units of the polymer, at least one of R¹, R², Ar¹, Ar² and Ar³ (when present) is substituted with hydroxyl. In some embodiments, at least one of R¹, R², Ar¹, Ar², and Ar³ (when present) is substituted with hydroxyl in at least 40 mole percent of the plurality of repeat units. In some embodiments, in 40 to 99 mole percent of the plurality of repeat units at least one of Ar¹, Ar², and Ar³ (when present) is substituted with hydroxyl, and in 1 to 60 mole percent of the plurality of repeat units at least one of Ar¹, Ar² and Ar³ is substituted with the acetal or ketal. A preferred acetal is —O—C(H)(R⁵)—OR⁶, wherein R⁵ is methyl and R⁶ is cyclohexyl. In some embodiments, each occurrence of Ar¹, Ar², and Ar³ is independently 1,3-phenylene or 1,4-phenylene.

When used in applications in which the polymer is exposed to acid to promote fragmentation, it may be desirable for the polymer to exclude robust linkages between the Ar¹ and Ar² rings. Thus, in some embodiments, Ar¹ and Ar² are not covalently linked with one another to form a ring structure that includes —Ar¹—O—C—O—Ar²—.

Specific examples of Ar¹, Ar², and Ar³ include unsubstituted or substituted 1,2-phenylene, unsubstituted or substituted 1,3-phenylene, unsubstituted or substituted 1,4-phenylene, unsubstituted or substituted 4,4′-biphenylene, unsubstituted or substituted 4,4″-p-terphenylene, unsubstituted or substituted 3,3″-p-terphenylene, unsubstituted or substituted 4,4″-m-terphenylene, unsubstituted or substituted 4,4″-p-terphenylene, unsubstituted or substituted 4,4″-o-terphenylene, unsubstituted or substituted 2,2″-o-terphenylene, unsubstituted or substituted 1,4-naphthylene, unsubstituted or substituted 2,7-naphthylene, unsubstituted or substituted 2,6-naphthylene, unsubstituted or substituted 1,5-naphthylene, unsubstituted or substituted 2,3-naphthylene, unsubstituted or substituted 1,7-naphthylene, unsubstituted or substituted 1,8-naphthylene, unsubstituted or substituted imidazo-2,4-ylene, 2,4-pyridylene, 2,5-pyridylene, unsubstituted or substituted 1,8-anthracenylene, unsubstituted or substituted 9,10-anthracenylene, unsubstituted or substituted 2,7-phenanthrenylene, unsubstituted or substituted 9,10-phenanthrenylene, unsubstituted or substituted 3,6-phenanthrenylene, unsubstituted or substituted 2,7-pyrenylene, unsubstituted or substituted 1,6-pyrenylene, unsubstituted or substituted 1,8-pyrenylene, unsubstituted or substituted 2,5-furanylene, unsubstituted or substituted 3,4-furanylene, unsubstituted or substituted 2,3-furanylene, unsubstituted or substituted 2,5-thiofuranylene, unsubstituted or substituted 3,4-thiofuranylene, unsubstituted or substituted 2,3-thiofuranylene, unsubstituted or substituted 2,5-oxazolylene, unsubstituted or substituted 2,7-fluorenylene, unsubstituted or substituted 2,5-benzofuranylene, unsubstituted or substituted 2,7-benzofuranylene, unsubstituted or substituted 5,7-benzofuranylene, unsubstituted or substituted 5,7-[1,3-benzoxazole], unsubstituted or substituted dithieno[3,2-b:2′,3′-d]thiophene, and unsubstituted or substituted 2,7-xanthenylene. In some embodiments, each occurrence of Ar¹, Ar², and Ar³ (when present) is independently 1,3-phenylene or 1,4-phenylene.

In the bis(aryl)acetal structure above, R¹ and R² are each independently hydrogen, unsubstituted or substituted C₁₋₁₈ linear or branched alkyl (e.g., methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 1methyl-2-propyl, diphenylmethyl, 2-phenylpropan-2-yl, 1,1-diphenylethan-1-yl, and triphenylmethyl), unsubstituted or substituted C₃₋₂₀ cycloalkyl (e.g., cyclopentyl, cyclohexyl, 1-norbornyl, 1-adamantlyl, 2-methylbicyclo[2.2.1]heptan-2-yl, 2-methyladamantan-2-yl); unsubstituted or substituted C₆₋₁₈ aryl (e.g., phenyl, 1-naphthyl, 2-naphthyl, anthracenyl), or unsubstituted or substituted C₃₋₁₈ heteroaryl (e.g., 2-imidazolyl, 4-imidazolyl, 2-pyridyl, 3-pyridyl, 4-pyridyl); and R¹ and R² are optionally covalently linked to each other to form a ring that includes —R¹—C—R²—. In some embodiments, at least one of R¹ and R² is hydrogen or methyl. In some embodiments, R¹ is hydrogen, and R² is selected from phenyl, ortho-methoxyphenyl, meta-methoxyphenyl, and para-methoxyphenyl. In some embodiments, R¹ is hydrogen and R² is unsubstituted or substituted phenyl. When R² is substituted phenyl, it can be substituted with a hydroxyl group, an acetal group, an ester group (including a lactone), or other such group that would be incompatible with polyacetal formation via acetal-generating polycondensation or would cause undesired polymer crosslinking. As described in a co-filed application, the present inventors have determined that such groups are tolerated in the Suzuki polycondensation reaction in which polyacetals are synthesized from the bis(aryl)acetal. Two specific examples of bis(aryl)acetal compounds in which R¹ and R² are covalently linked to each other to form a ring that includes —R¹—C—R²—

are

Specific examples of bis(aryl)acetals include

Examples of X—Ar^(a)—X, B_(x)—Ar³—B_(x), and B_(x)—Ar³—X include

In a very specific embodiment of the bis(aryl)acetal structure above, Y is B^(x); each occurrence of B^(x) is

Ar¹ and Ar² are 1,4-phenylene; R¹ is hydrogen; and R² is phenyl.

Synthesis of the bis(aryl)acetal is described in co-filed U.S. patent application Ser. No. 13/943,232, filed Jul. 16, 2013.

The method utilizes a catalyst to polymerize the bis(aryl)acetal, optionally in combination with the bis(leaving group)arylene. In general, the catalyst is a Suzuki coupling catalyst. Reviews of Suzuki polycondensation and resulting polymers have been published by Schlüter et al. in Macromol. Rapid Commun. 2009, 30, 653 and J. Polym. Sci. Part A. Polym. Chem. 2001, 39, 1533. The present inventors have determined that particularly active catalysts for polymerization include those having the structure

wherein each occurrence of R¹⁴ is independently unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, or unsubstituted or substituted ferrocenyl; R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹ are, independently, hydrogen, C₁₋₆ linear or branched alkyl, C₃₋₆ cycloalkyl, or phenyl; and Z is selected from the group consisting of fluorine, chlorine, bromine, iodine, cyano (—CN), cyanate (—OCN), isocyanate (—NCO), thiocyanate (—SCN), isothiocyanate (—NCS), nitro (—NO₂), nitrite (—ON═O), azide (—N═N⁺═N⁻), and hydroxyl. Methods of preparing such catalysts are described in C. C. C. Johansson Seechurn, S. L. Parisel, and T. J. Calacot, J. Org. Chem. 2011, 76, 7918-7932, where the catalysts are used for bimolecular coupling. In a very specific embodiment of the method, in the bis(aryl)acetal structure, Y¹ and Y² are each B^(x), each occurrence of B^(x) is

Ar¹ and Ar² are 1,4-phenylene; Ar³ is 1,3-phenylene substituted with hydroxyl or an acetal, —O—C(H)(R⁵)—OR⁶, wherein R⁵ is methyl and R⁶ is cyclohexyl; R¹ is hydrogen; R² is phenyl, ortho-methoxyphenyl, meta-methoxyphenyl, or para-methoxylphenyl; and in the catalyst structure above, each occurrence of R¹⁴ is t-butyl; R¹⁵ is methyl; R¹⁶, R¹⁷, R¹⁸, and R¹⁹ are hydrogen; and Z is chlorine.

The concentration of the catalyst can vary depending on factors including the bis(aryl)acetal structure, the catalyst structure, and the polymerization reaction temperature, but the mole ratio of catalyst to bis(aryl)acetal is generally 1×10⁻⁶:1 to 0.05:1, specifically 1×10⁻⁵:1 to 0.01:1, more specifically 1×10⁻⁴:1 to 0.005:1.

In addition to the catalyst, a base is used in the polymerization reaction. A wide variety of bases can be employed, as long as they do not decompose the catalyst or the bis(aryl)acetal. Suitable bases include carbonate salts (such as lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, ammonium carbonate, and substituted ammonium carbonates, as well as the corresponding hydrogen carbonate salts), phosphate salts (including lithium phosphate, sodium phosphate, potassium phosphate, rubidium phosphate, cesium phosphate, ammonium phosphate, and substituted ammonium phosphates, as well as the corresponding hydrogen phosphate salts), and acetate salts (including lithium acetate, sodium acetate, potassium acetate, rubidium acetate, cesium acetate, ammonium acetate, and substituted ammonium acetates).

Suitable bases further include carboxylic acid salts (other than acetate salts) such as salts of formate, fluoroacetate, and propionate anions with lithium, sodium, potassium, rubidium, cesium, ammonium, and substituted ammonium cations; metal dihydroxides such as magnesium dihydroxide, calcium dihydroxide, strontium dihydroxide, and barium dihydroxide; metal trihydroxides such as aluminum trihydroxide, gallium trihydroxide, indium trihydroxide, thallium trihydroxide; non-nucleophilic organic amines such as triethylamine, N,N-diisopropylethylamine (Hünig's base), 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU); bis(silyl)amide salts such as the lithium, sodium, and potassium salts of bis(trimethylsilyl)amide; alkoxide salts such as the lithium, sodium, and potassium salts of t-butoxide; and 1,8-bis(dimethylamino)naphthalene (PROTON-SPONGE™).

In some embodiments, the base is selected from potassium carbonate, cesium carbonate, potassium phosphate, sodium acetate, and combinations thereof. In some embodiments, the base comprises potassium phosphate.

The base and particularly hydrophilic bases can, optionally, be employed in the presence of a phase transfer catalyst and/or water and/or an organic solvent.

The base is typically used in an amount of at least one equivalent per equivalent of bis(aryl)acetal. In some embodiments, the base amount is 1 to 10 equivalents per equivalent of bis(aryl)acetal, specifically 2 to 6 equivalents per equivalent of bis(aryl)acetal.

The polymerization reaction can be conducted in a solvent. Suitable solvents include, for example, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, methyl t-butyl ether, diethylether, ethanol, propanol, n-butanol, s-butanol, t-butanol, dimethylformamide, toluene, acetonitrile, and combinations thereof. The solvent can further include water to facilitate the dissolution of inorganic salts, if any, or to improve conversion yield.

The polymerization can be conducted over a wide range of temperatures. In some embodiments, the polymerization is conducted at a temperature of 0 to 100° C. Within this range, the polymerization temperature can be 10 to 80° C., specifically 20 to 70° C.

The time required for polymerization can be determined by the skilled person without undue experimentation and will depend on factors including the identity of the bis(aryl)acetal, the identity of the bis(leaving group)arylene (if any), the identity of the catalyst, and the polymerization temperature. In some embodiments, the polymerization time is 30 minutes to 200 hours. Within this range, the polymerization time can be 10 to 100 hours, specifically 20 to 50 hours.

In some embodiments, the substructure

within any of the repeat units

or

is selected from the group consisting of

In some embodiments, the substructure

within any of the repeat units

is selected from the group consisting of

In some embodiments, the polymer is end capped by addition of one or more compounds that will react with terminal B^(x) or X groups of the polymer chain. In these embodiments, the monomer further comprises an endcapping agent selected from Ar⁴—X, Ar⁴—B^(x), and combinations thereof, wherein Ar⁴ is an unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene, and X and B^(x) are defined above. Specific examples for endcapping compounds include

In some embodiments, at least one endcapping agent is added after substantial completion of the polymerization reaction (i.e., after completion of reaction of bifunctional monomer) as a method to (1) reduce the halogen and/or boron content of the polymer and/or (2) to adjust polymer properties that include solubility and substrate adhesion. In some embodiments, suitable amounts range from 0.01 equivalents to 5 equivalents with respect to the initial monomer concentration, more specifically, 0.1 equivalents to 0.3 equivalents with respect to the initial monomer concentration.

In some embodiments, the endcapping reagent is added at the beginning or during the course of the polymerization as a method to (1) limit molecular weight, (2) reduce the halogen and/or boron content of the final polymer and/or (3) to adjust specific polymer properties that include solubility and substrate adhesion. Suitable amounts of the end capping reagent dependent on the targeted molecular weight and/or relative reactivity of the end capping reagent in comparison with monomer reactivity and range from 0.0001 equivalents to 1 equivalent with respect to initial monomer concentration.

The polyacetals produced by the present method are useful compounds due to their ability to fragment into at least two smaller molecules upon treatment with Brønsted or Lewis acids or upon electron impact or ionization. Such fragmentation can be used to alter the physicochemical properties (including solubility, aggregation state, glass transition temperature, melting point, and vapor pressure) of materials or formulations comprising the polyacetals. The polyacetals can be used in various articles and applications, including biological applications (e.g., pH-dependent delivery of active agents including pharmaceuticals), prodrugs and amplified drug release, microencapsulation and extended release applications (e.g., encapsulation of active agents for pharmaceutical or agricultural applications); diagnostic applications; signal amplification; photoresists for lithography, including lithography using ultraviolet (UV) wavelengths, extreme ultraviolet wavelengths (EUV), and electron beams, photoresist topcoats and underlayers; electronic devices including patternable light emitting devices (OLED/PLED), photovoltaic devices, organic thin-film transistors (TFTs), and molecular logic gates; photographic applications such as detection or imaging of radioactive compounds or UV radiation; and pH indicators.

The invention is further illustrated by the following examples.

GENERAL PROCEDURES

All solvents and reagents were obtained in commercially available qualities purum, puriss. or p.a. Dry solvents were obtained from in-house purification/dispensing system (hexane, toluene, tetrahydrofuran and diethyl ether) or purchased from Sigma-Aldrich, Fisher Scientific, or Acros.

Proton nuclear magnetic resonance (¹H-NMR) spectra (500 megahertz (MHz) or 400 MHz) were obtained on a Varian VNMRS-500 or VNMRS-400 spectrometer at 30° C. unless otherwise noted. The chemical shifts were referenced to tetramethylsilane (TMS) (δ=0.00) in CDCl₃, Benzene-d₅ (7.15) in Benzene-d₆ or tetrahydrofuran-d₇ (THF-d₇; δ 3.58 (used) and 1.73) in THF-d₈. If necessary, peak assignment was carried out with the help of COSY, HSQC or NOESY experiments. ¹³C-NMR spectra (125 MHz or 100 MHz) were obtained on a Varian VNMRS-500 or VNRMS-400 spectrometer, chemical shifts were solvent or standard signals (0.0—TMS in CDCl₃, 128.02—Benzene-d₆, 67.57 (53.37)—THF-d₈). If NMR was used for quantification purposes, single scan experiments or relaxation delays of ≧30 seconds were used.

Polymers were analyzed as follows. Weight average molecular weight (M_(n)) and number average molecular weight (M_(w)) and polydispersity (D=M_(w)/M_(n)) were determined by gel permeation chromatography. Two milligrams of the polymer sample was dissolved in 1.0 milliliter of uninhibited THF, followed by 0.22 micrometer membrane filtration and injection of 50 microliters of the resulting sample into an Agilent 1100 Series GPC system coupled to a refractive index detector. The following analysis conditions were used: column: 300×7.5 mm Agilent PLgel 5 μm MIXED-C; column temperature 35° C.; mobile phase: THF; flow 1 mL/min; detector temperature: 35° C.

Melting points (T_(m)) and glass transition temperatures (T_(g)) were obtained by differential scanning calorimetry (DSC) using a TA Instruments Q2000 DSC, using T4 calibration (Indium, Sapphire). Approximately 5 milligrams of each sample was weighed into a TZero Aluminum DSC pan with lid. A heat/cool/heat temperature profile at a ramp rate of 10° C./minute was used, under nitrogen purge. Samples were heated from room temperature to 150° C., cooled to −90° C., and heated again to 150° C. Data analysis was performed using TA Universal Analysis software.

Thermal decomposition temperatures (T_(d)) were measured by thermogravimetric analysis (TGA) on a TA Instruments Q50001R with Infrared accessory and autosampler. Approximately 5 milligrams of each sample was weighed into a TA high-temperature platinum pan. Samples were loaded at room temperature (using autosampler) and ramped to 600° C. at 10° C./minute under a constant dried air purge. Data analysis was performed using TA Universal Analysis software.

PREPARATIVE EXAMPLE 1

In the example outlined below, 30% of the repeat units contain —OCHVE and 70% of the repeat units contain a free phenol.

pBEBA-2,4-DBP-CHVE (30%). Under nitrogen, 2,2′-(((phenylmethylene)bis(oxy))bis(4,1-phenylene))-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (8.000 grams, 15.14 millimoles, 1.000 equivalent) and 2,4-dibromo-1-(1-(cyclohexyloxy)ethoxy)benzene (1.632 gram, 4.316 millimole, 0.285 equivalents) were combined in a round bottom flask. Under nitrogen, in a separate vial, potassium phosphate (10.06 grams, 47.4 millimole, 3.13 equivalents) was dissolved in deoxygenated water (13 milliliters). Under nitrogen, in a separate vial, Pd(crotyl)(P(tBu)₃)Cl (6.0 milligrams, 15 micromole, 0.001 equivalent) was dissolved in degassed 1,4-dioxane (200 microliters). 1,4-dioxane (50 milliliters) was added to the main reaction vessel followed by the potassium phosphate solution. The mixture was vigorously stirred, until both phases were well-blended. The catalyst solution was then added via cannula. The reaction mixture was stirred for 5 hours, then 2,4-dibromophenol (2.537 grams, 10.07 millimoles, 0.665 equivalent) was added. The reaction mixture was stirred vigorously overnight. After an additional 20-22 hours, phenyl boronic acid end cap (0.277 gram, 2.27 millimoles, 0.15 equivalent) was added. The reaction was stirred vigorously overnight. After an additional 20-24 hours, bromobenzene end cap (477 microliters, 4.54 millimole, 0.30 equivalents) was added. The reaction was stirred vigorously overnight.

The reaction mixture was worked up by adding 50 milliliters diluted brine and 100 milliliters ethyl acetate followed by shaking in an extraction funnel. The aqueous layer was removed and the remaining organic phase was further washed with brine (1×50 milliliters). The organic phase was transferred into a round bottom flask equipped with reflux condenser, a saturated aqueous solution of sodium diethyldithiodicarbamate (˜10 milliliters) was added, and the mixture was vigorously stirred under reflux for 60 minutes. The organic phase was separated, dried over magnesium sulfate, and filtered through a three layered plug of CELITE™ diatomaceous earth (˜0.25 inch on top), FLORISIL™ activated magnesium silicate (0.15 inch in middle) and silica gel (0.15 inch on bottom). The crude product was fully eluted with 200 milliliters ethyl acetate and the combined organic phases were washed with deionized water (5×50 milliliters) and concentrated on the rotary evaporator. The residue was taken up in ethyl acetate (˜50 milliliters) with toluene (5-10 milliliters). The polymer was precipitated by drop-wise addition to stirred methanol (700 milliliters). Once the addition was complete, the suspension was stirred for 30 minutes and then allowed to settle. The precipitate was collected by filtering through a pre-washed disposable filter cartridge and air dried. The residue was again taken up in ethyl acetate (˜50 milliliters) with toluene (5-10 milliliters), and the precipitation procedure repeated twice. After the final precipitation, the filter cake was dried under high vacuum oven at ˜65° C. overnight. The product was obtained in form of a colorless powder (5.55 grams, 91% polymerization yield). DSC: T_(g) at 136.1° C.; TGA: T_(d) (5% weight loss) at 270.9° C.; GPC (against PS standard): M_(n)=6.44 kilodaltons (kDa), M_(w)=13.4 kDa, D=2.08; ¹H NMR (500 MHz, THF-d₈) δ 8.28-8.16 (2.8%), 7.75-7.62 (9.4%), 7.60-7.16 (40.0%), 7.13-6.80 (24.7%), 5.43-5.31 (1.1%), 3.53-3.37 (1.2%), 1.71-1.06 (23.0%); [Integration ratio δ 8.20/5.36 71:29]; ¹³C NMR (101 MHz, THF-d₈) δ 156.74, 156.44, 156.40, 154.83, 154.42, 139.16, 137.33, 136.41, 135.90, 135.40, 134.07, 134.04, 133.99, 133.36, 133.34, 133.32, 131.72, 131.42, 129.95, 129.82, 129.68, 129.61, 129.38, 129.36, 129.33, 128.54, 128.31, 127.88, 127.51, 127.10, 126.99, 118.79, 118.52, 118.49, 118.47, 118.44, 117.55, 117.52, 117.48, 117.38, 117.21, 109.32, 101.30, 101.25, 101.20, 101.15, 101.03, 100.26, 84.37, 75.08, 67.57, 34.38, 33.23, 26.75, 24.85, 21.71.

PREPARATIVE EXAMPLE 2

pBEBA-2,4-DBP (0%). Under nitrogen, 2,2′-(((phenylmethylene)bis(oxy))bis(4,1-phenylene))-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (6.000 grams, 11.36 millimole, 1.000 equivalent) and 2,4-dibromophenol (2.718 gram, 10.79 millimole, 0.950 equivalent) were combined in a round bottom flask. Under nitrogen, in a separate vial, potassium phosphate (7.54 gram, 35.5 millimoles, 3.13 equivalents) were dissolved in deoxygenated water (10 milliliters). Under nitrogen, in a separate vial, Pd(crotyl)(P(tBu)₃)Cl (4.5 milligrams, 11.4 micromoles, 0.001 equivalents) was dissolved in degassed 1,4-dioxane (200 microliters). 1,4-dioxane (45 milliliters) was added to the main reaction vessel followed by the potassium phosphate solution. The mixture was vigorously stirred, until a homogeneous emulsion formed. The catalyst solution was then added via cannula. The reaction was stirred vigorously overnight. After an additional 20-22 hours, phenyl boronic acid end cap (208 milligrams, 1.70 millimole, 0.15 equivalent) was added. The reaction was stirred for an additional 7-8 hours, then bromobenzene end cap (358 microliters, 3.41 millimoles, 0.30 equivalent) was added. The reaction was stirred vigorously overnight.

The reaction was worked up by adding 50 milliliters diluted brine and 100 milliliters ethyl acetate followed by shaking in an extraction funnel. The aqueous layer was removed and the remaining organic phase was further washed with brine (1×50 milliliters). The organic phase was transferred into a round bottom flask equipped with reflux condenser, a saturated aqueous solution of sodium diethyldithiodicarbamate (˜10 milliliters) was added, and the mixture was vigorously stirred under reflux for 60 minutes. Brine (30 milliliters) was added, the organics phase was isolated, dried over magnesium sulfate, and filtered through a three layered plug of CELITE™ diatomaceous earth (˜0.25″ on top), FLORISIL™ activated magnesium silicate (0.15″ in middle) and silica gel (0.15″ on bottom). The crude product was fully eluted with ethyl acetate (200 milliliters) and the combined organic phases were concentrated on the rotary evaporator. The residue was taken up in ethyl acetate (˜50 milliliters) with toluene (5-10 milliliters). The polymer was precipitated by drop-wise addition to stirred methanol (700 milliliters). Once the addition was complete, the suspension was stirred for 30 minutes and then allowed to settle. The precipitate was collected by filtering through a pre-washed disposable filter cartridge and air dried. The residue was again taken up in ethyl acetate (˜50 milliliters) with toluene (5-10 milliliters), and the precipitation procedure repeated twice. After the final precipitation, the filter cake was dried under high vacuum oven at ˜65° C. overnight. The product was received in form of a colorless powder (3.68 g, 88% polymerization yield). DSC: T_(g) at 147.7° C.; TGA: T_(d) (5% weight loss) at 291.0° C.; GPC (against PS standard): M_(n)=5.98 kDa, M_(w)=13.5 kDa, D=2.26; ¹H NMR (400 MHz, THF-d₈) δ 8.23-8.16 (4.8%), 7.73-7.17 (61.7%), 7.09-6.98 (22.7%), 6.93-6.75 (11.3%); ¹³C NMR (101 MHz, THF-d₈) δ 156.46, 154.81, 139.19, 136.41, 134.06, 134.04, 133.41, 133.38, 131.43, 130.32, 129.95, 129.70, 129.62, 129.39, 129.37, 129.34, 128.88, 128.32, 127.88, 127.52, 127.13, 118.48, 118.44, 118.27, 117.57, 117.54, 117.40, 101.27, 101.15, 101.08, 101.03, 67.57.

PREPARATIVE EXAMPLE 3

pBEBA-2,4-DBR-CHVE/Ac (50%/50%). 2,2′-(((phenylmethylene)bis(oxy))-bis(4,1-phenylene))-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (6.0100 gram, 11.55 millimoles, 1.0 equivalent) and 2,4-dibromo-5-(1-(cyclohexyloxy)ethoxy)phenyl acetate (4.7845 gram, 10.97 millimoles, 0.950 equivalent) were combined in a round bottom flask and brought into a nitrogen glove box. Inside the nitrogen glove box, in a separate vial, potassium phosphate (7.6675 gram, 36.1 millimoles, 3.13 equivalents) was dissolved in degassed water (10 milliliter). In a separate small vial, Pd(crotyl)(P(tBu)₃)Cl catalyst (4.6 milligram, 11.55 micromoles, 0.001 equivalent) was dissolved in 1,4-dioxane (200 microliters). 1,4-Dioxane (45 milliliters) was added to the reaction round bottom flask followed by the potassium phosphate solution. The mixture was vigorously stirred with a large stir bar until both phases were well blended. The catalyst solution was then added via pipette. The reaction was stirred vigorously for two days at room temperature. Phenyl boronic acid end cap (211 milligrams, 1.73 millimoles, 0.15 equivalents) was added and the reaction was stirred vigorously for an additional 7 hours. Bromobenzene end cap (0.36 milliliters, 3.46 millimoles, 0.30 equivalent) was added and the reaction was stirred vigorously for an additional 17 hours.

The reaction was worked up outside of the glove box by adding water (20-25 milliliters), brine (20-30 milliliters) and ethyl acetate (100 milliliters). The organic layer was separated and stirred with saturated solution of disodium dithiodicarbamate (3 milliliters) and water (10 milliliters) at 80° C. for 1 hour. Once cooled, brine (20 milliliters) was added and the organic layer was separated and the aqueous phase re-extracted with ethyl acetate (1×50 milliliters). The combined organic phases were washed with brine (1×50 milliliters), dried over magnesium sulfate and filtered through a three layered plug of CELITE™ diatomaceous earth, FLORISIL™ activated magnesium silicate, and silica gel. The polymer was fully eluted with ethyl acetate (˜200 milliliters) and the filtrate was concentrated under reduced pressure. The residue was taken up in ethyl acetate (˜50 milliliters) and with toluene (5-10 milliliters). The polymer was precipitated by adding drop-wise to 700 milliliters vigorously stirring hexanes. Once the addition was complete, the suspension was stirred for 30 minutes and then allowed to settle. The precipitate was collected by and air dried. The precipitate was dissolved in ethyl acetate (˜50 milliliters) with toluene (5-10 milliliters) and the precipitation procedure was repeated. The final product was bottled and dried in vacuum oven at ˜65° C. overnight. The final product with fully intact acetate groups was obtained in the form of a colorless solid in a yield of 4.528 grams. GPC (polystyrene standard): M_(n)=5.30 kDa, M_(w)=10.0 kDa, D=1.9; ¹H-NMR (400 MHz, THF-d₈) δ 7.70-7.59 (5.9%), 7.52-7.20 (22.1%), 7.12-6.81 (17.0%), 5.48-5.15 (2.4%), 3.52-3.39 (2.5%), 2.07-1.90 (7.4%), 1.69-0.97 (42.8%).

Superimposed ¹H-NMR spectra of the polymer in acetone-d₆ without (solid line) or with (dashed line) D₂O are presented in FIG. 1. The spectra superimpose perfectly. Phenolic protons in similar polymers typically appear at a chemical shift of δ≈8.2 but are not present in the NMR spectra, indicating that all of the phenol groups bear protecting groups. The identical spectrums further indicate that no acidic protons (such as phenolic protons) are present in the polymer. In addition, a peak at δ 2.00 is visible, which is not visible for similar polymers that do not contain acetate side chains.

Superimposed ¹H-NMR spectra of untreated polymer (solid line) and NaOH-treated polymer (dashed line, some EtOAc signals) in THF-d₈ are presented in FIG. 2. The spectrum of the NaOH-treated polymer shows deprotection of acetyl groups (absence of peak at δ 2.00) and appearance of free phenol groups (presence of peak at δ 8.2).

COMPARISONS OF CATALYSTS AND BASES

These examples illustrate the activities of different Suzuki coupling catalysts in the copolymerization below, utilizing a difficult-to-polymerize dihalide monomer:

Inside a nitrogen-purged glovebox, catalyst solutions were prepared having the compositions summarized in Table 1. In each case, the solvent was 1,4-dioxane.

TABLE 1 Catalyst total volume Solution Compound(s) milligrams micromoles (μL) 1 s-Phos¹ 7.8 18.9 1,000 Palladium acetate 1.7 7.6 2 Pd(PPh₃)₄ 8.8 7.6 1,000 3 Pd(dppf²)Cl₂ 5.5 7.6 1,000 4 cataCXium ™ A³ 6.8 18.9 1,000 Palladium acetate 1.7 7.6 5 tri-t-butylphosphine 3.8 18.9 1,000 Palladium acetate 1.7 7.6 6 Pd(crotyl)(PtBu₃)Cl⁴ 3.0 7.6 1,000 ¹s-Phos is 2-Dtcyclohexylphosphino-2′,6′-dimethoxybiphenyl (CAS Reg. No. 657408-07-6). ²dppf is bis(diphenylphosphino)ferrocene (CAS Reg. No. 72287-26-4). ³cataCXium ™ A is di(1-adamanty1)-n-butylphosphine (CAS Reg. No. 321921-71-5). ⁴Pd(crotyl)(PtBu₃)Cl is chloro(crotyl)(tri-tert-butylphosphine)palladium(II) (CAS Reg. No. 1334497-00-5).

2,2′-(((Phenylmethylene)bis(oxy))bis(4,1-phenylene))bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (1.520 grams, 2.877 millimoles) and the dibromide shown in the equation above (1.494 grams, 2.871 millimoles, 0.998 equivalents) were taken up in 10.5 mL of 1,4-dioxane. 55 microliter aliquots of this mixture were distributed to 18 vials, labeled A-R. To vials A-F K₃PO₄ (101 milligrams, 476 micromoles, 3.14 equivalents) was added. To vials G-L, Cs₂CO₃ (197 milligrams, 606 micromoles, 4 equivalents) was added. To vials A-L, degassed water (121 microliters) was added. To vials M-R, degassed NaOH (aq.), (5 M, 121 microliters, corresponding to 606 micromoles NaOH, 4 equivalents) was added.

Twenty microliters of catalyst solution 1 was added to vials A, G, M. Twenty microliters of catalyst solution 2 was added to vials B, H, N. Twenty microliters of catalyst solution 3 was added to vials C, J, O. Twenty microliters of catalyst solution 4 was added to vials D, K, P. Twenty microliters of catalyst solution 5 was added to vials E, L, Q. Twenty microliters of catalyst solution 6 was added to vials F, M, R. In each case, the added catalyst corresponded to 0.001 equivalents palladium.

Reactions were run over night at 60° C., phase separated, filtered through a plug of silica (fully eluted with ethyl acetate), concentrated, and analyzed by GPC. The results are summarized in Table 2. All experiments with Pd(crotyl)(PtBu₃)Cl as a catalyst show higher M_(w) values compared to the other catalysts tested under identical conditions, and M_(n) are also higher except that the s-Phos/PdOAc2 catalyst of Experiment M produced a slightly higher Mn value than did the Pd(crotyl)(PtBu₃)Cl catalyst of Experiment R.

TABLE 2 Experiments at 60° C. Experiment Catalyst Base M_(n) M_(w) PDI A s-Phos/PdOAc2 K₃PO₄ 5507 9784 1.7766 B Pd(PPh3)4 K₃PO₄ 1060.9 1656.5 1.5614 C Pd(dppf)Cl2 K₃PO₄ 668.53 958.96 1.3188 D CataCXium ™ A/ K₃PO₄ 3872.7 5521.1 1.4257 PdOAc2 E (tBu)3P/Pd(OAc)2 K₃PO₄ 761.5 1997.9 2.6236 F Pd(crotyl)(PtBu3)Cl K₃PO₄ 7115 16040 2.2544 G s-Phos/PdOAc2 Cs₂CO₃ 4429.3 7251 1.637 H Pd(PPh3)4 Cs₂CO₃ 954.63 1439.2 1.5076 I Pd(dppf)Cl2 Cs₂CO₃ 726.79 1093 1.5039 J CataCXium ™ A/ Cs₂CO₃ 3575.5 5019.9 1.404 PdOAc2 K (tBu)3P/Pd(OAc)2 Cs₂CO₃ 479.68 958.61 1.9985 L Pd(crotyl)(PtBu3)Cl Cs₂CO₃ 5565.6 9983 1.7937 M s-Phos/PdOAc2 NaOH 5675.5 17714 3.1211 N Pd(PPh3)4 NaOH 3229 5234.9 1.6212 O Pd(dppf)Cl2 NaOH 812.03 1638.8 2.0181 P CataCXium ™ A/ NaOH 726.04 2277.7 3.1371 PdOAc2 Q (tBu)3P/Pd(OAc)2 NaOH 1573.4 3862.9 2.4551 R Pd(crotyl)(PtBu3)Cl NaOH 5395.9 23953 4.4391

Experiments A and F were repeated, except at room temperature rather than 60° C. The results, presented in Table 3, show that the Experiment F′ at room temperature conditions, using Pd(crotyl)(PtBu₃)Cl catalyst and K₃PO₄ base, produced substantially higher Mn and Mw values than the Experiment A′ at room temperature conditions. Pd(crotyl)(PtBu₃)Cl catalyzed the reaction to give a molecular weight of about 7.7 kilodaltons (kDa), which was ideal for the targeted application (photoresists), whereas s-Phos/PdOAc₂ catalyst produced a polymer with insufficient molecular weight for use in photoresists.

TABLE 3 Experiments at Room Temperature Experiment Catalyst Base M_(n) M_(w) PDI A′ s-Phos/PdOAc2 K₃PO₄ 1264 2399.1 1.898 F′ Pd(crotyl)(PtBu3)Cl K₃PO₄ 4862.9 7753.7 1.5944 

The invention claimed is:
 1. A method of forming a polymer, the method comprising: reacting a monomer in the presence of a catalyst and a base to form a polymer; wherein the monomer comprises a bis(aryl)acetal having the structure

wherein Y¹ and Y² are each independently chloro, bromo, iodo, mesylate, tosylate, triflate, or B^(x), wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar¹ or Ar² via a boron atom; Ar¹ and Ar² are each independently unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene; and R¹ and R² are each independently hydrogen, unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl; unsubstituted or substituted C₆₋₁₈ aryl, or unsubstituted or substituted C₃₋₁₈ heteroaryl; and R¹ and R² are optionally covalently linked to each other to form a ring that includes —R¹—C—R²—; wherein when one of Y¹ and Y² is chloro, bromo, iodo, triflate, mesylate, or tosylate, and the other of Y¹ and Y² is B^(x), the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², R¹, and R² are defined above, and each occurrence of Ar¹, Ar², R¹, and R² is defined independently; wherein when Y¹ and Y² are each B^(x), the monomer further comprises a bis(leaving group)arylene having the structure X—Ar³—X wherein each occurrence of X is independently chloro, bromo, iodo, triflate, mesylate, or tosylate; wherein Ar³ is unsubstituted or substituted C₆₋₁₈ arylene, or unsubstituted or substituted C₃₋₁₈ heteroarylene; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently; and wherein when Y¹ and Y² are each independently selected from chloro, bromo, iodo, triflate, mesylate, or tosylate, the monomer further comprises a bis(boron-containing functional group)arylene having the structure B^(x)—Ar³—B^(x) wherein each occurrence of B^(x) is independently a boron-containing functional group bonded to Ar³ via a boron atom; and wherein the polymer comprises a plurality of repeat units having the structure

wherein Ar¹, Ar², Ar³, R¹, and R² are defined above, and each occurrence of Ar¹, Ar², Ar³, R¹, and R² is defined independently.
 2. The method of claim 1, wherein one of Y¹ and Y² is chloro, bromo, iodo, triflate, mesylate, or tosylate, and the other of Y¹ and Y² is B^(x).
 3. The method of claim 1, wherein Y¹ and Y² are each B^(x), and the monomer further comprises the bis(leaving group)arylene having the structure X—Ar³—X.
 4. The method of claim 1, wherein Y¹ and Y² are each independently selected from chloro, bromo, iodo, triflate, mesylate, or tosylate, and the monomer further comprises the bis(boron-containing functional group)arylene having the structure B^(x)—Ar³—B^(x).
 5. The method of claim 1, wherein each occurrence of B^(x) is independently selected from —BF₃ ⁻M⁺, wherein each occurrence of M⁺ is independently an alkali metal cation, or an unsubstituted or substituted ammonium ion; —B(OH)₂; and

wherein R³ and R⁴ are each independently C₁₋₁₈ alkyl, C₃₋₁₈ cycloalkyl, or C₆₋₁₈ aryl; and R³ and R⁴ are optionally covalently linked to each other to form a ring that includes —R³—O—B—O—R⁴—.
 6. The method of claim 1, wherein at least one of Ar¹, Ar², and Ar³ is substituted with at least one functional group selected from the group consisting of hydroxyl, acetals, ketals, esters, and lactones.
 7. The method of claim 1, wherein in at least one of the repeat units of the polymer, at least one of R¹, R², Ar¹, Ar² and Ar³ is substituted with hydroxyl.
 8. The method of claim 1, wherein Ar¹ and Ar² are not covalently linked with one another to form a ring structure that includes —Ar¹—O—C—O—Ar².
 9. The method of claim 1, wherein the catalyst or a pre-catalyst thereof has the structure

wherein each occurrence of R¹⁴ is independently unsubstituted or substituted C₁₋₁₈ linear or branched alkyl, unsubstituted or substituted C₃₋₁₈ cycloalkyl, unsubstituted or substituted C₆₋₁₈ aryl, or unsubstituted or substituted ferrocenyl; R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹ are, independently, hydrogen, C₁₋₆ linear or branched alkyl, C₃₋₆ cycloalkyl, or phenyl; and Z is selected from the group consisting of fluorine, chlorine, bromine, iodine, cyano (—CN), cyanate (—OCN), isocyanate (—NCO), thiocyanate (—SCN), isothiocyanate (—NCS), nitro (—NO₂), nitrite (—ON═O), azide (—N═N⁺═N⁻), and hydroxyl.
 10. The method of claim 9, wherein Y is B^(x); each occurrence of B^(x) is

Ar¹ and Ar² are 1,4-phenylene; Ar³ is 1,3-phenylene substituted with hydroxyl or an acetal, —O—C(H)(R⁵)—OR⁶, wherein R⁵ is methyl and R⁶ is cyclohexyl; R¹ is hydrogen; R² is phenyl, ortho-methoxyphenyl, meta-methoxyphenyl, or para-methoxylphenyl; each occurrence of R¹⁴ is t-butyl; R¹⁵ is methyl; R¹⁶, R¹⁷, R¹⁸, and R¹⁹ are hydrogen; and Z is chlorine. 